Abstract: An energy saving particle swarm optimization (ESPSO) algorithm is proposed to improve the coverage of directional sensor networks with mobile nodes. Since the existing algorithms consider the maximum movement distance of each node as a constant constraint and only treat the position and sensing angle of each node as adjustable parameters which may result in redundant movement of the nodes, the movement distance of each node is added as a tuple in the particles of particle swarm optimization (PSO) algorithm to adaptively adjust the movement distance and introduce mutation in the particles. Experimental results show that the proposed algorithm can significantly reduce the energy cost compared with absorbing PSO algorithm under the same node movement constraint while achieving the same coverage optimization.